In the art of glass container manufacture, it is typical standard practice to utilize an individual section machine in which a number of machine sections are mounted side-by-side on a single machine bed to operate in synchronization with each other while being independently adjustable. In the utilization of a press and blow method of glass container production in an individual section machine, discrete molten glass gobs are fed into an upwardly-open blank mold after which the mold is closed at the top by a baffle. Although a single gob mold may be utilized, it is more common to have a plurality of molds in a section, such as double gob or triple gob arrangements. Then, separate molten glass gobs are fed simultaneously to each mold in the section.
For each mold, a vertically-elongated pressing plunger is driven upwardly to press the molten glass into the blank mold and into an adjacent neck ring mold, forming a parison from the glass gob. The plunger is then downwardly retracted and the blank mold and the baffle are temporarily removed so that the parison can be removed and inverted by the neck ring mold from the blank to a laterally adjacent blow mold station where the final formation of the glass container occurs by a blowing operation.
For each blank mold, there is a separate mechanism for supporting and driving a pressing plunger for initially forming the parison in cooperation with the mold, and this mechanism includes a vertically-elongated cylinder mounted to support an axially-oriented piston rod within the cylinder's longitudinal bore. The pressing plunger is removably mounted by means of an adapter to the upper end of the piston rod whereby the plunger can be cycled through its pressing operation.
The piston and piston rod are an integral structure driven to cycle linearly by pressurized air fed into the cylinder's chamber. The plunger is cooled during its gob pressing operation by a relatively high-pressure air flow directed through the cylinder's bottom end structure and upwardly through a rigid air tube on which the hollow piston vertically slides. The air stream directed upwardly through the air tube and into the piston bore enters an elongated distributor projecting internally within the hollow plunger. The air flow is dispersed by the distributor within the plunger and returned downwardly through an array of exhaust passages or ports circumferentially arranged, usually in the bottom flange of the distributor. The exhaust air then passes through communicating openings in component structure of the adapter utilized to retain the plunger in its operative position on the piston rod.
The upper end of the cylinder casing serves as a collecting chamber for the exhaust air which may then be emitted outwardly through a laterally mounted exhaust manifold. The exhaust manifold in a plural gob section may be a unitary structure extending across a bank of aligned cylinders with a sidewall opening in each upper cylinder casing in sealed air flow communication with the exhaust manifold. Vertically-extending exhaust conduits may be utilized to direct the exhaust air flow downwardly for emission into the section box beneath the cylinders.
In the type of glass container forming machine heretofore generally described, a continuing problem is the control of machine performance to obtain consistent quality in the glass containers produced at a high production rate. Variance of conditions associated with the machine's operation will significantly affect the finished product. The failure to hold within a proper range such parameters as gob temperature, plunger dwell, rate of heat removal from the plunger by the cooling air flow, air pressure within the cylinder, and gob size or weight can result in the formation of rejected or inferior containers.
There have been many approaches to controlling one or more of the conditions associated with the machine's operation, none of which have been entirely satisfactory. One common method involves the operator of the machine making manual adjustments to various controls in accordance with his prior experience and the results of his visual inspection of the quality of glass containers delivered from the machine, the object being to correct, through trial and error, those conditions contributing to the noticed defects whereby subsequently produced containers will be of higher quality. Another method utilized, particularly addressing the control of gob weight for the purpose of having each gob contain sufficient glass to form an acceptable container, has been to weigh the finished product and utilize this after-attained information to adjust incoming gob weight in accordance with the findings in the weighing operation.
A recent development and significant advancement in controlling gob weight recognizes the direct relationship between the extent of advancement of the plunger into the gob and the size of the gob being pressed. This requires knowing the position of the plunger and the extent of its penetration into the gob as it occurs, whereby plunger position can be correlated with gob weight and gob weight can be continuously adjusted through the use of appropriate control station means of interpreting the received data and automatically controlling the timing of gob shearing, etc. To accomplish the foregoing, a proximity sensor has been mounted on the cylinder of a plunger mechanism to detect vertical movement of an angled surface on the plunger assembly and, by the variance in proximity of the angled surface, the position of the plunger has been extrapolated.
The foregoing method, while a significant move toward a worthy objective, fails to take into account other parameters or conditions subject to fluctuation within the equipment during its operation which, unless they are also monitored and controlled, prevent accurate control of gob weight by simply monitoring plunger position at full penetration.